# Backdrop

- Page: https://jiguang132.com/resources/material-ui/docs/backdrop
- Resource: Material UI (https://jiguang132.com/resources/material-ui.md)
- All guides: https://jiguang132.com/resources/material-ui/docs.md

Dim a background while a foreground task or overlay is active.

This guide covers Material UI Core with the default Emotion engine; extensions and additional demos are explicitly classified.

## Use case and business boundary

Backdrop alone does not implement dialog semantics, focus trapping or asynchronous work.

## Native composition and scope

`Backdrop`

Preserve native Material UI composition and types; do not substitute JGuang UI/Base UI/Radix APIs. Example entries are not extra components.

## Native installation and initialization

```bash
npm install @mui/material@9.4.0 @emotion/react@11.14.0 @emotion/styled@11.14.1
```

Use native npm and Emotion, not an invented JGuang UI Registry URL. Place examples inside native ThemeProvider; choose CssBaseline or ScopedCssBaseline for the project. Inspect React, existing providers, lockfile and SSR first. Never overwrite files or conceal peer conflicts. This batch verified React 19.2.8; React 18 and below require matching react-is. See the included bilingual setup guide.

## Practical native parameters

These selected parameters are not a flattened universal API. Preserve the native declaring owner, slot structure, nullable values and generics.

| Owner.prop | Practical role | Declaration source |
| --- | --- | --- |
| `Backdrop.open` | Controlled native visibility; it does not fetch data or execute actions. | `Backdrop` |
| `Backdrop.transitionDuration` | Native transition duration in milliseconds or supported auto value. | `Backdrop` |

## Runnable native examples

Machine keys select example entries, not universal variant props. Native demo JSX/data stay unchanged; JGuang-authored acceptance fixtures are explicitly labelled.

- Example · `SimpleBackdrop` · upstream native demo

## Actual usage example

Unmodified pinned native demo; copy its required local helper files together.

```tsx
import * as React from 'react';
import Backdrop from '@mui/material/Backdrop';
import CircularProgress from '@mui/material/CircularProgress';
import Button from '@mui/material/Button';

export default function SimpleBackdrop() {
  const [open, setOpen] = React.useState(false);
  const handleClose = () => {
    setOpen(false);
  };
  const handleOpen = () => {
    setOpen(true);
  };

  return (
    <div>
      <Button onClick={handleOpen}>Show backdrop</Button>
      <Backdrop
        sx={(theme) => ({ color: '#fff', zIndex: theme.zIndex.drawer + 1 })}
        open={open}
        onClick={handleClose}
      >
        <CircularProgress color="inherit" />
      </Backdrop>
    </div>
  );
}

```

## Example dependency boundaries

`react`, `@mui/material/Backdrop`, `@mui/material/CircularProgress`, `@mui/material/Button`

Direct Icons/System/Utils example imports require their matching 9.4.0 packages. Relative data/helpers are part of the example closure, not extra components. Remote images and simulated operations do not supply a backend.

## Pinned upstream API metadata reference

These tables retain the upstream metadata, not a newly inferred generic type system. Conditional generics, inherited props and callback details are defined by the source declarations below. Theme defaults may override metadata defaults.

### Backdrop

```tsx
import Backdrop from '@mui/material/Backdrop';
import { Backdrop } from '@mui/material';
```

Native inheritance: `Fade`. Parent/DOM props are not fabricated as additional own props.

| Prop | Required | Upstream metadata type / constraint | Metadata default |
| --- | --- | --- | --- |
| `open` | yes | `bool` | — |
| `children` | no | `node` | — |
| `classes` | no | `object` | — |
| `component` | no | `elementType` | — |
| `invisible` | no | `bool` | `false` |
| `slotProps` | no | `{ root?: func \| object, transition?: func \| object }` | `{}` |
| `slots` | no | `{ root?: elementType, transition?: elementType }` | `{}` |
| `sx` | no | `Array<func \| object \| bool> \| func \| object` | — |
| `transitionDuration` | no | `number \| { appear?: number, enter?: number, exit?: number }` | — |


## Native source declarations

Declarations/imports are extracted from pinned source without flattening unions or external inheritance. Original English comments/types are source reference, not a claim of translated upstream prose. Shared types stay in their native packages.

### vendor/src/Backdrop/Backdrop.d.ts

```ts
import * as React from 'react';

import { SxProps } from '@mui/system';

import { FadeProps } from '../Fade';

import { TransitionProps } from '../transitions/types';

import { Theme } from '../styles';

import { BackdropClasses } from './backdropClasses';

import { OverridableComponent, OverrideProps } from '../OverridableComponent';

import { CreateSlotsAndSlotProps, SlotComponentProps, SlotProps } from '../utils/types';

export interface BackdropSlots {
  /**
   * The component that renders the root.
   * @default 'div'
   */
  root: React.ElementType;
  /**
   * The component that renders the transition.
   * [Follow this guide](/material-ui/transitions/#transition-slots) to learn more about the requirements for this component.
   * @default Fade
   */
  transition: React.ElementType;
}

export interface BackdropComponentsPropsOverrides {}

export interface BackdropTransitionSlotPropsOverrides {}

export type BackdropSlotsAndSlotProps = CreateSlotsAndSlotProps<
  BackdropSlots,
  {
    /**
     * Props forwarded to the transition slot.
     * By default, the available props are based on the div element.
     */
    root: SlotProps<'div', BackdropComponentsPropsOverrides, BackdropOwnerState>;
    /**
     * Props forwarded to the transition slot.
     * By default, the available props are based on the [Fade](https://mui.com/material-ui/api/fade/#props) component.
     */
    transition: SlotComponentProps<
      React.ElementType<TransitionProps>,
      TransitionProps & BackdropTransitionSlotPropsOverrides,
      BackdropOwnerState
    >;
  }
>;

export interface BackdropOwnProps
  extends Partial<Omit<FadeProps, 'children'>>, BackdropSlotsAndSlotProps {
  /**
   * The content of the component.
   */
  children?: React.ReactNode;
  /**
   * Override or extend the styles applied to the component.
   */
  classes?: Partial<BackdropClasses> | undefined;
  /**
   * If `true`, the backdrop is invisible.
   * It can be used when rendering a popover or a custom select component.
   * @default false
   */
  invisible?: boolean | undefined;
  /**
   * If `true`, the component is shown.
   */
  open: boolean;
  /**
   * The system prop that allows defining system overrides as well as additional CSS styles.
   */
  sx?: SxProps<Theme> | undefined;
  /**
   * The duration for the transition, in milliseconds.
   * You may specify a single timeout for all transitions, or individually with an object.
   */
  transitionDuration?: TransitionProps['timeout'] | undefined;
}

export interface BackdropTypeMap<
  AdditionalProps = {},
  RootComponent extends React.ElementType = 'div',
> {
  props: AdditionalProps & BackdropOwnProps;
  defaultComponent: RootComponent;
}

type BackdropRootProps = React.HTMLAttributes<HTMLDivElement> & BackdropComponentsPropsOverrides;

export declare const BackdropRoot: React.FC<BackdropRootProps>;

declare const Backdrop: OverridableComponent<BackdropTypeMap>;

export type BackdropProps<
  RootComponent extends React.ElementType = BackdropTypeMap['defaultComponent'],
  AdditionalProps = {},
> = OverrideProps<BackdropTypeMap<AdditionalProps, RootComponent>, RootComponent> & {
  component?: React.ElementType | undefined;
};

export interface BackdropOwnerState extends BackdropProps {}
```

## Post-install acceptance

Run strict types, production build and real interactions. Check keyboard labels/focus, disabled/error/read-only semantics where natively supported, both themes, narrow screens and reduced motion. Verify callbacks against the real host data; do not declare installation complete from copying a prompt. Initialization fixtures also require server HTML and warning-free hydration.

## Source and license

https://github.com/mui/material-ui/tree/809a7717b4c050ba3f69b75300689f07c050a16e

MIT · @mui/material@9.4.0. Vendor originals and license are preserved. Full original upstream prose remains in vendor/docs and is not represented as fully translated.

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